Hydroquinone monosulfonate in direct positive photographic developers



p 1954 H. D. RUSSELL ET AL HYDROQUINONE MONOSULFONATE IN DIRECT POSITIVE PHOTOGRAPHIC DEVELOPERS Filed June 27, 1951 w w 5 m s m WEDWOQX mo m M m 0 M m d l New m 7/ m r 9 H G 0w y QV/ vs B QM/ 90 W M 3 u 07 A o a l3 HEN. 2

Patented Apr. 13, 1954 HYDROQUINONE MONOSULFONATE 1N DIRECT POSITIVE PHOTOGRAPHIG DEVELOPERS Harold D. Russell and Grant M. Haist, Rochester, N. Y., assignors to EastmanKodak Company, Rochester, N. Y., a corporation of New Jersey Application June 27, 1951, Serial No. 233,774

3 Claims. 1

This invention relates to photography and particularly to developers for direct positive photographic processes.

In Fallesen U. S. Patent 2,497,875, a method is described for making direct positive photographs with an internal latent image type emulsion by developing the exposed emulsion in an aerial fogging developer with access to oxygen.

Ives U. S. Patent 2,588,982, describes a method for developing direct positive images in an exposed internal latent image emulsion by the use of hydrazine or certain hydrazine derivatives so that no special aeration technique for production of the positive image is required.

In processing emulsions of the type described in the Fallesen patentit is difficult to compound developers which produce a range of contrasts. Control of contrast is desirable if the emulsion is used for continuous tone reproduction.

We have found that contrast may be varied in emulsions of the type disclosed in the Fallesen patent and in Davey and Knott U. S. Patent 2,592,250 by the use of developers containing one or more hydroquinone sulfonates, e. g., hydroquinone monosulfonate, but substantially free of unsubstituted hydroquinone. The developers preferably also contain N-methyl-p-aminophenol sulfate and one of the hydrazines disclosed in the Ives U. S. Patent 2,588,982, or Bean and Russell U. S. application Serial No. 218,072, filed March 28, 1951, now Patent No. 2,604,400.

The accompanying drawing shows characteristic curves of the images produced using various developers according to our invention.

The photographic emulsion used in the process of our invention is a gelatino-silver halide emulsion such as a silver bromide emulsion, a silver bromoiodide emulsion or a silver chloroiodide emulsion. It need not contain optical sensitizing dyes although certain sensitizing dyes may be added to it for the purpose of optical sensitizing or for promoting reversal. The emulsion should be undigested or if digested, the digestion should B is heated to 70 C. and A, cold, added to B with constant shaking, digested for 20 minutes at 50 C., and allowed to cool slowly. C is added after being allowed to swell for 20 minutes in water, drained and melted. The emulsion is then set and washed.

An internal latent image emulsion, that is, one which forms the latent image mostly inside the silver halide grains, as described on pages 296 and 297 of Mees The Theory of the Photographic Process, 1942, is especially useful for the process of our invention.

Most of the internal latent image emulsions are silver bromoiodide emulsions of high iodide content, preferably containing at least 10%20% of iodide. Burtons emulsion is an emulsion of this type, having a silver iodide content of approximately 40% of the content of silver halide. It is not absolutely essential, however, for the emulsion to contain silver iodide.

An internal latent image emulsion made as described in Davey and Knott U. S. Patent 2,592,250, may also be used according to our invention. This emulsion is prepared by first forming in the absence of ammonia and in one or more stages silver salt grains consisting at least partly of a silver salt which is more soluble in water than silver bromide, subsequently converting the grains to silver bromide or silver bromoiodide and if the silver iodide content of the emulsion is less than 6% calculated on the total silver halide, treating such grains with an iodine compound to bring the silver iodide up to at least 6%, ripening preferably in the absence of ammonia and then either washing out some of the soluble salts or washing out the whole of the soluble salts, followed by the addition of solu ble salts such as soluble choride or bromide. An example of an emulsion made in this Way is as follows:

Solution No. 1:

be carried out without the use of sulfur sensi- Inert gelatm 20 grams 0 tizers. An emulsion of this type is that known K01 20 grams at 40 as Burtons emulsion, described in Wall, Photo- Water 560 graphic Emulsions, 1929, pages 52 and 53. Solution No. 2: Burtons emulsion is made as follows: KCl 100- grams a Water 520 cc at 45 A. Silver nitrate g 100 Water cc Solution NO. 3:

Ammonia-to form clear solution. AgNO3 195 grams} at B. Potassium bromide g Water 520 Potassium iodide g 50 Solution No. 4:

Soft gelatin g 20 KBr grams Water cc 1000 KI 40 grams at 45 C. C. Dry gelatine .g... 250 55 Water 500 cc.

Run solutions Nos. 2 and 3 simultaneously into solution No. 1 in a vessel, taking 90 seconds to do this. Then ripen for '1 minute at 45 0. Next add 235 grams of inert gelatine (dry) Ihen ripen at 45 C. for 15 minutes during which time the gelatine dissolves. Set and shred the emulsion and then wash until free from all soluble bromide and then add about 150 cc. of 10% solution of KCl (by weight), and then add water to make 3 liters.

An internal latent image type of silver halide emulsion may be defined as one which, when a test portion is exposed to alight intensity scale for a fixed time between and 1 second, and developed for 4 minutes at 20 C. in the ordinary, "surface developer (Example I), exhibits a maximum density not greater than the maximum density obtained when the same emulsion is equally exposed and developed for 3 minutes at 20 C. in an internal type developer (Example II). Preferably the maximum density obtained with the surface developer is not greater than the maximum density obtained when the same emulsion is developed in the internal type developer. Stated conversely, an internal latent image emulsion, when developed in an internal type developer (Example II) exhibits a maximum density at least 5, and preferably at least 10', times the maximum density obtained when the same emulsion is exposed in the same way and developed in a surface developer (Example I).

Our process is carried out by exposing the internal latent image emulsion to an object or image and then placing the exposed emulsion layer directly in a silver halide developing solu tion containing an alkali metal salt of sulfonated hydroquinone, e. g, sodium hydroquinone monosulfonate, potassium hydroquinone monosulfonate, or sodium hydroquinone disulfonate. The developing solution should also contain N-methyl-p-aminophenol sulfate, and by varying the cdncentration of this ingredient, direct positive images of varying contrast can be produced. The developing solution. should also contain one of the hydrazines disclosed in the Ives Patent 2,588,982 or the Bean and Russell U. S. application Serial No. 218,072, preferably an aryl hydrazine such as phenylhydrazine hydrochloride, a-naphthylhydrazine, l-naphthylhydrazine-l-sulfonic acid, p- (fl-methyl sulfonamidoethyl) phenylhydrazine, or p-methyl sulfonamido ethyl hydrazine hydrochloride. The developing solution should have a pH of from 10 to 13, the most satisfactory range being from pH 10.5 to pH 11.5. The developin solution should contain no unsubstituted hydrcquinone Example I p-Hydroxyphenylglycine -Q g 10 Sodium carbonate (crystals) g 100 Water 1201 liter Development time, 4 min. at 20 CL An internaltype developer, that is, one which develops an image inside the grains of an internal latent image emulsion is the following:

Example II I-Iydroquinone g.. N-methyl-p-aminophenol sulfate g 15 Sodium sulfite (anhydrous) g 50 Potassium bromide g 10 Sodium hydroxide g 25 Sodium thiosulfate (crystals) g Water to 1 liter Development time, 3 min. at 20 C.

The following examples illustrate developing solutions which may be used according to our invention:

Example III p- (fi-Methylsulfonamido ethyl) -phenyl hydrazine g 2 N-methyl-p-aminophenol sulfate g 10 Sodium hydroquinone monosulfonate.. g 15 Sodium sulfite g S-methyl benzotriazole g 0.25 Sodium hydroxide g 8 Water to 1 liter Example IV p (,B-Methylsulfonamido ethyl) -phenyl hy- V drazine g 2 Nmethylp-aminophenol sulfate g 2 Sodium hydroquinone monosulfonateg 15 Sodium sulfite g 75 5--nethyl benzotriazole g 0.25

Sodium hydroxide g 4.6 Water to 1 liter Example V An emulsion made as described in the Davey and Knott U. S. Patent 2,592,250 was coated on a support, dried and exposed on an intensity scale sensitometer to 3000" K. tungsten illumination and developed for 1 minutes at 75 F. in the developer of Example III. A direct positive image having the characteristic curves shown in A of the drawing was produced.

The variation in contrast which may be produced according to our invention is illustrated by reference to the characteristic curves shown in the drawing. Development in the formula of Example III produced curve A. Development in the solution of Example IV, under the same conditions as those specified in Example V, produced curve D. A mixture of Example III with l part of the developer of Example IV produced curve B. A mixture of equal parts of the formulas of Examples III and IV produced curve C. By using either of the developers of Examples III or IV or the mixtures indicated, developers were produced containing respectively 10, 8, 6 and 2 grams per liter of N-methyl-p-aminophenol sulfate. The concentration of sodium hydroquinone monosulfonate remainedthe same in each case, The useful gamma produced in this way-varies from about 0.9 in curve A to about 1.6 in curve D.

hydroquinone '(HO-CtHi-OH) per liter of" solution.

It will be understood that the examples and modificationsincluded herein are illustrative only and that our invention, is to be taken as limited only-by thescope of the appended claims. Weclaim: 1. A developing solution for direct positive silver halide emulsions comprising N-met hylpaminophenol sulfate, an aryl hydrazine,--and-at Z least one alkali metal hydroquinone sulfonate and substantially free of unsubstituted hydroquinone.

2. A developing solution for direct positive silver halide emulsions comprising N-methyl-paminophenol sulfate, p-(fl-methyl sulfonamidoethyl) -phenyl hydrazine and sodium hydroquinone monosulfonate and substantially free of unsubstituted hydroquinone.

3. The method of obtaining a direct positive image in a silver halide emulsion layer, which comprises exposing to light rays to which the emulsion is sensitive, a silver halide emulsion layer a, test portion of which upon exposure to a light intensity scale for a fixed time between and 1 second and development for 3 minutes at 20 C. in the following internal type developer (II) Water to 1 liter gives a maximum density at least 5 times the maximum density obtained when the equally exposed silver halide emulsion isdeveloped for 4 minutes at 20 C. in the following surface developer (I) Grams p-Hydroxyphenylglycine 10 Sodium carbonate Water to 1 liter References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,458,376 Henn Jan. 4, 1949 2,497,875 Fallesen Feb. 21, 1950 2,497,876 Fallesen et a1 Feb. 21, 1950 2,563,785 Ives Aug. 7, 1951 2,572,903 Bates Oct. 30, 1951 2,604,400 Bean et al July 22, 1952 

1. A DEVELOPING SOLUTION FOR DIRECT POSITIVE SILVER HALIDE EMULSIONS COMPRISING N-METHYL-PAMINOPHENOL SULFATE, AN ARYL HYDRAZINE, AND AT LEAST ONE ALKALI METAL HYDROQUINONE SULFONATE AND SUBSTANTIALLY FREE OF UNSUBSTITUTED HYDROQUINONE.
 3. THE METHOD OF OBTAINING A DIRECT POSITIVE IMAGE IN A SILVER HALIDE EMULSION LAYER, WHICH COMPRISES EXPOSING TO LIGHT RAYS TO WHICH THE EMULSION IS SENSITIVE, A SILVER HALIDE EMULSION LAYER A TEST PORTION OF WHICH UPON EXPOSURE TO A LIGHT INTENSITY SCALE FOR A FIXED TIME BETWEEN 1/100 AND 1 SECOND AND DEVELOPMENT FOR 3 MINUTES AT 20* C. IN THE FOLLOWING INTERNAL TYPE DEVELOPER (II): 